1. Field of the Invention
The present invention relates to a window taking in and blocking outside light for use in automobiles, buildings, etc., and more particularly to a new light control window having a light control capability using a layer having a magneto-optic effect.
2. Discussion of the Background
Windows of buildings such as office buildings and plants usually have separate means, such as shutters and curtains, so that the inside of the buildings cannot be seen from the outside. Typically, the shutter and curtain mechanically transfer alight shield to transmit or block light. In addition, a window of an automobile has the same means.
On the other hand, the following methods have been tried to perfectly shield the window of a building and automobile without covering the whole area thereof:
(1) a method of fitting two pieces of an inexpensive film polarizer to a window and mechanically rotating the polarizers to transmit or block light;
(2) a method of electrically transmitting and blocking light, using a liquid crystal plate between glasses of a window instead of rotating the polarizers; and
(3) a method of using electrochromism technologies, e. g., a technology controlling a transmitted light volume by forming a thin film of WO3 or NiO2 on a window, and installing upper and under transparent electrodes applying a voltage of a few volts to color the window.
However, the above-mentioned conventional technologies have the following problems:
The first method can control a light volume, but needs a space larger than the size of the window to mechanically rotate the light polarizers, which have a light transmittance of 50%;
The second method does not need a space for rotation and can block light at a comparatively high speed, but does not solve the low light transmittance of the first method. In addition, application of the voltage has to be continuous to block light, and further the liquid crystal has to be included with a precise interval between the glasses, which is difficult for a large area; and
The third method, although having a higher light utilization efficiency and being more improved than the first and second methods, has the following drawbacks:
(1) WO3 becomes blue and NiO2 becomes brown when colored, and these colors are not preferable for windows;
(2) application of the voltage also has to be continuous in order to decrease the transmitted light volume by coloring and a large electric power is necessary for a large area, which is not practical; and
(3) the light transmittance is about 70% when fully opened and 20% when completely closed, which is insufficient. In particular, the 20% light transmittance when the window is completely closed is a large drawback in practical use.
Because of these reasons, a need exists for a window having a light control capability of continuosly and easily changing light transmittance at a high speed without the need of a mechanical transfer.